JPH05243118A - Detection of position and device therefor - Google Patents

Abstract

PURPOSE:To conduct an incident light beam positioning in a highly precise manner by a method wherein the deviation from the predetermined position of incidence on the mask of a flux of light is detected, the deviation of incident position is corrected by positioning the flux of light against the mask, and the positional deviation between the mask and a wafer is detected by the above-mentioned flux of light. CONSTITUTION:The relative positional relation of the alignment of a mask and a wafer is detected by a light projecting means, i.e., an alignment head 14 and a mask 18. After their positional relation has been adjusted by a driving means, their position are detected. The position of luminous fluxes is adjusted by driving the alignment head 14 in such a manner that the integral value of the quantity-of-light distribution on the surface of licensor 12 formed by the luminous light 26-1, which passed through the AA mark 20M1 on the surface of the mark 18 and the AA mark 20W1 on the surface of a wafer 19, and the luminous flux 26-2, which passed through the AA mark 20M2 on the surface of the mask 18 and the AA mark 20W2 on the surface of the wafer 19, among the luminous fluxes sent from the projection means. The incident position on the mask 18 of the luminous flux 15 sent from the above-mentioned position is adjusted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting method and a position detecting apparatus using the same. For example, in a proximity type exposure apparatus for manufacturing a semiconductor element, a so-called stepper, etc., a mask or reticle (hereinafter referred to as "mask") is used. .)
It is suitable for performing relative positioning between the mask and the wafer when exposing and transferring a fine electronic circuit pattern formed on the first object surface such as the wafer onto the second object surface such as the wafer. The present invention relates to a position detecting method and a position detecting device using the same.

[0002]

2. Description of the Related Art Conventionally, in an exposure apparatus for manufacturing semiconductor devices, relative alignment between a mask and a wafer has been an important factor for improving performance. Particularly in the recent alignment of the exposure apparatus, in order to achieve high integration of semiconductor elements, it is required to have alignment accuracy of, for example, submicron or less.

In many alignment devices, a so-called alignment pattern (also referred to as "alignment mark") for alignment is provided on the mask and the wafer surface on a so-called scribe line, and position information obtained from them is used. Both sides are aligned. As an alignment method at this time, for example, US Pat.
7969 and Japanese Patent Laid-Open No. 56-157033 use a zone plate as an alignment pattern, irradiate the zone plate with a light beam, and detect the position of the focal point of the light beam emitted from the zone plate on a predetermined surface. Etc.

Further, in US Pat. No. 4,311,389, an alignment pattern is provided on the mask surface so that the diffracted light has the same optical effect as a so-called cylindrical lens.
On the surface of the wafer, a diffracted light is further provided with a dot array alignment pattern that maximizes the amount of diffracted light of a predetermined order when the mask and the wafer match, and detects the light flux through both alignment patterns. By doing so, the relative positional relationship between the mask and the wafer is detected.

In addition to the above, the present applicant has previously filed Japanese Patent Application No. 63-22.
No. 6003, when detecting a relative positional deviation between a first object as a mask and a second object as a wafer, there are two sets of alignment marks each having a lens action on the first object surface and the second object surface. A physical optical element is provided, a light beam is emitted from a light projecting unit including a laser to the physical optical element, and diffracted light sequentially diffracted by the physical optical element is guided to a sensor (detection unit). Then, by determining the relative distance value between the two light spots on the sensor surface, the first
The amount of relative displacement between the object and the second object is detected.

At this time, the light projecting means is housed in one housing (alignment head) together with the detecting means for receiving the light sequentially diffracted by the two sets of physical optical elements provided on the object surface for position detection. There is.

[0007]

Generally, the width of the mask on which the alignment mark is provided and the scribe line on the wafer surface is about 50 μm to 100 μm. The width of this scribe line is 250 μm to 500 μm on the reticle surface for a stepper with a projection magnification of 5 times, and 50 μm to 100 μm for an X-ray equal-magnification contact exposure (proximity) device. It is provided in. In this way, the alignment pattern is set within the scribe line width.

In order to efficiently irradiate the light beam (light beam) from the alignment head (light projecting means) onto the alignment pattern provided in such a small area, the light beam diameter is reduced to a size corresponding to the size of the alignment pattern. There is a need. Furthermore, it is necessary to irradiate the light beam at a correct position with respect to the alignment pattern.

In general, when the alignment pattern is irradiated with a light beam inaccurately, the light amount (signal light) detected by the sensor is reduced. If the luminous flux diameter is sufficiently larger than the size of the alignment pattern, the alignment pattern can be irradiated with a substantially uniform light amount distribution.

However, when the luminous flux is efficiently radiated and the luminous flux is radiated to the circuit pattern area other than the area of the alignment pattern, unnecessary scattered light from the circuit pattern becomes noise. Therefore, in order to prevent this, the alignment pattern It is necessary to irradiate with a light beam having a substantially equal size corresponding to the size of.

In general, when the diameter of the light beam is reduced in this way, the light amount distribution of the light beam becomes uneven on the alignment pattern surface on the mask (reticle) surface.

Further, when the irradiation position of the light flux on the alignment pattern is largely displaced, the spot position of the diffracted light (that is, the displacement information of the mask and the wafer) obtained from the alignment pattern when the displacement of the mask and the wafer exists to some extent. This is different from the case where the irradiation position of the light flux on the alignment pattern is not displaced. That is, if the irradiation position of the light beam with which the alignment pattern is irradiated is displaced, an error will occur in alignment detection.

Therefore, by improving the positioning accuracy of the light beam (light projecting means) and the alignment mark (first object or second object) and setting the optimum light beam diameter, it is possible to improve the alignment accuracy. However, if an attempt is made to improve the positioning accuracy of the light beam incident on the alignment mark surface only with a mechanical system, it will be difficult to achieve long-term stability due to the complexity and size of the system. ..

According to the present invention, the positioning of the light beam from the light projecting means with respect to the physical optical element, which is the alignment mark provided on the first object or the second object, is accurately performed by a simple method with high accuracy, thereby achieving mechanical accuracy and assembly. An object of the present invention is to provide a position detection method and a position detection device using the same, which can reduce the accuracy and the like, and can perform relative position detection of a first object and a second object thereafter with high accuracy.

[0015]

According to the position detecting method of the present invention, a light beam having a predetermined intensity distribution is applied to a mask alignment pattern, and signal light from the mask is used to detect a gap between the mask and the wafer. In the method of detecting the positional deviation of, detecting the deviation from a predetermined position of the incident position of the light flux on the mask using the signal light,
It is characterized in that the deviation of the incident position is corrected by aligning the light flux with respect to the mask, and the misalignment between the mask and the wafer is detected by the aligned light flux.

Further, the position detecting device of the present invention, when the first object and the second object are opposed to each other to detect the relative position, the first object and the second object are placed on the object plane of at least one of 1,
A second two pairs of physical optical elements are formed in the position detection direction and in a direction orthogonal to the position detection direction, respectively, and the first pair of physical optical elements of the light beam from the light projecting means and the other object surface are optically coupled. The pair of luminous fluxes A that have been actuated are guided to a predetermined surface, the light amount distribution of the pair of luminous fluxes A on the predetermined surface is detected, and the second pair of physical optical elements and the other A pair of light beams B which have been optically acted on the object plane are guided to a predetermined surface, and
The feature is that the positions of the light projecting means and the one of the objects are set by detecting the light quantity distribution of the pair of light beams B.

At this time, the pair of first and second pairs of physical optical elements are marks for detecting relative positions of the first object and the second object.

Another position detecting apparatus of the present invention is arranged such that when the first object and the second object are opposed to each other and relative position detection is performed, the position detection device is arranged on the first object surface and on the second object surface, respectively. Two pairs of physical optical elements are formed on at least one of the object planes in a position detection direction and a direction orthogonal thereto, and a pair of light beams from the light projecting means is formed on the first object plane and the second object plane. The pair of diffracted lights generated at this time are guided to a predetermined surface through the physical optical element of the above, and the luminous flux position of the diffracted light on the predetermined surface is detected by the detection means, thereby the first object and the second object. When performing relative position detection with respect to an object, a first pair of physical optical elements formed on the one object surface of the light flux from the light projecting means and the other object surface are optically affected, The light intensity distribution of the pair of diffracted lights incident on the first detection surface of the detection means is detected and the second
Of the pair of physical optical elements and the object surface of the other, and detects the light intensity distribution of the pair of diffracted light incident on the second detection surface of the detection means to detect the light projection means and the light projection means. First
It is characterized in that the position of the object or the second object is set.

Particularly, in the present invention, a pair of physical optical elements as alignment marks are arranged close to each other, and are arranged symmetrically, for example, so that the light quantity loss when the incident light beam is diffracted becomes substantially equal. Then, the light amount distributions of the pair of diffracted lights generated from the pair of physical optical elements are detected, the light amount distributions at this time are compared, and the light flux from the light projecting means is adjusted so that the respective light amount distributions have a predetermined relationship with each other. It is characterized in that it is aligned with a physical optical element, that is, a first object or a second object, and that this light beam is accurately incident on a predetermined position.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a perspective view of an essential part of a first embodiment of the present invention, FIGS. 2 and 3 are enlarged explanatory views of a part of FIG. 1, and FIGS. It is an explanatory view of the principle of detection. Note that FIG. 1 shows a case where the present invention is applied to an X-ray exposure apparatus for performing equal-magnification printing by a proximity method, a reduction projection exposure apparatus such as an optical stepper, or the like.

In the figure, 1 is a light source, and in the case of an optical stepper, a light source emitting a coherent light beam such as a semiconductor laser, a He-Ne laser, an Ar laser or a light source or a super light source emitting a non-coherent light beam such as a light emitting diode. It consists of a light source with intermediate properties such as a luminescent diode (SLD). Reference numeral 2 denotes a collimator lens, which causes the light beam from the light source 1 to enter the lens system 5 as a parallel light beam. The lens system 5 makes the incident light beam have a desired beam diameter, and then reflects it by a mirror 6 to pass through an Xray-resistant window 7 (which is arranged when an Xray source is used as a light source for exposure) and as a first object. AA alignment mark (hereinafter referred to as "AA mark") for detecting the positional deviation on the mask 18 surface of
Say. ) 20M or an AF alignment mark (hereinafter referred to as “AF mark”) 21M for detecting the surface spacing. The light source 1, the collimator lens 2, the lens system 5 and the like constitute a light projecting means.

The AA mark 20M and the AF mark 21M are provided at four locations on the scribe line around the mask 18. Reference numeral 19 denotes a wafer as a second object, which is arranged in proximity to the mask 18 (distance: 10 μm to 100 μm), and the surface of the wafer 19 should be aligned with the mask 18.
The A mark 20W is provided on the scribe line. 1 for AA mark 20M, 20W and AF mark 21M
It consists of a physical optical element such as a one-dimensional or two-dimensional zone plate.

Reference numeral 10 denotes a light receiving lens, which collects diffracted light 16 of a predetermined order which has passed through the AA mark 20M and the AF mark 21M on the surface of the mask 18 on the surface of the light receiving means 11. The light receiving means 11 is configured by providing two line sensors, that is, an AA line sensor 12 as a first detection surface for detecting a positional deviation and an AF line sensor 13 as a second detection surface for detecting a surface distance on the same substrate. There is. Reference numeral 14 is an alignment head, which is configured to be driven by a driving unit (not shown).

FIG. 2 is an explanatory view of the AA marks 20M and 20W and the AF mark 21M provided on the surface of the mask 18 and the wafer 19.

FIG. 3 shows an optical path of a light beam passing through each mark on the surface of the mask 18 and the wafer 19. As shown in FIG. 2, the AA mark 20M as the first pair of physical optical elements
Is composed of two AA marks 20M1 and 20M2, and the AA mark 20W as a pair of physical optical elements is two AA marks.
The AF mark 21M, which is composed of the marks 20W1 and 20W2 and serves as a second pair of physical optical elements, has two A rays for incidence.
It is composed of F marks 21M1, 21M3 and two AF marks 21M2, 21M4 for ejection. The second pair of physical optical elements in the AF mark 21M are the AF marks 21M1 and 21M2 or the AF marks 21M3 and 21M.
It refers to 4.

Note that no AF mark is provided on the surface of the wafer 19 and light 0-order reflected (regularly reflected) on the surface of the wafer 19 is used.

As shown in FIG. 3, AA marks 20M1 and 2A2 are provided.
0W1 corresponds, and also AA mark 20M2 and 20
W2 corresponds to each AA mark 20M1, 20M1
Two diffracted lights (hereinafter referred to as “AA diffracted lights”) 26-1 and 2 by the respective marks of the two light beams 15 incident on 0M2.
6-2 is set so as to move on the surface of the AA line sensor 12 in correspondence with the positional deviation.

Further, the light beam 15 incident on the AF marks 21M1 and 21M3 is reflected by the surface of the wafer 19 and is reflected by the AF mark 21M.
Two diffracted lights (hereinafter, referred to as “AF diffracted lights”) 27-1 and 27-2 emitted from 2, 21M4 are set to move on the surface of the AF line sensor 13 in accordance with the surface spacing.

It should be noted that in FIG. 3, each incident light 15 uses a light beam in one common beam emitted from the light source 1.

The position detecting apparatus of the present invention aligns the mask and the wafer with a light projecting means, that is, the alignment head 1.
4 and the mask 18 are detected, and the positional relationship between the two is adjusted by the driving means. However, before that, the positional deviation detecting method and surface spacing according to the present invention are performed. The principle of the detection method will be described.

First, in the present invention, the mask 18 and the wafer 1
The in-plane position detection method relative to 9 will be described with reference to FIG.

FIG. 4 shows the state in which the optical path is expanded when viewed from a direction perpendicular to the position detection direction (alignment direction) in FIG. 3 and perpendicular to the surface normal of the mask 18 and the wafer 19.

In the figure, the same elements as those shown in FIGS. 1 to 3 are designated by the same reference numerals. Further, although the incident light beam is reflected and diffracted by the AA mark on the surface of the wafer 19, it is shown in an equivalent transmission diffracted state in FIG.

Reference numeral 20M1 is an AA mark provided on the mask 18, and 20W1 is an AA mark provided on the wafer 19 to form a single mark for obtaining the first signal. Reference numeral 20M2 is an AA mark provided on the mask 18 and 20W2 is provided on the wafer 19 to form a single mark for obtaining the second signal. Reference numerals 26-1 and 26-2 denote AA diffracted lights for the first and second signals, and 32 denotes a first-order focus surface, which has a conjugate relationship with the light receiving means 11 with respect to the light receiving lens 10.

Now, the distance from the wafer 19 to the primary focus surface 32 is L, the distance between the mask 18 and the wafer 19 is g, A
The focal lengths of the A marks 20M1 and 20M2 are f _a1 and f, respectively.
_a2, and Δσ the relative positional deviation amount of the mask 18 and the wafer 19, the displacement from matching state of the light beam centroid of AA diffracted light 26-1 and 26-2 in this case with each S _1, S _2.

The light beam 15 incident on the mask 18 is a plane wave for convenience, and the reference numerals are as shown in the figure. Displacement amounts S ₁ and S ₂ of the light beam centroids of the AA diffracted lights 26-1 and 26-2
Is the focal points F ₁ , F ₂ and A of the AA marks 20M1, 20M2
1 and the straight line connecting the optical axes of the A marks 20W1 and 20W2
It is geometrically determined as an intersection with the next focus plane 32.
Therefore, the displacement amount S of the light beam center of gravity of each of the AA diffracted lights 26-1 and 26-2 with respect to the relative positional deviation between the mask 18 and the wafer 19.
_{In order that 1} and S ₂ are in mutually opposite directions, the signs of the optical imaging magnifications of the AA marks 20W1 and 20W2 can be made opposite to each other.

Quantitatively,

[0038]

[Equation 1] The shift magnifications are β ₁ = S ₁ / Δσ, β ₂ = S ₂ /
It can be defined as Δσ. Therefore, in order to set the shift magnification to the opposite sign,

[0039]

[Equation 2] Should be satisfied. Of these, one of the practically appropriate configuration conditions
As one example, there is a condition of L >> | _fa1 | _fa1 / _fa2 <0 | _fa1 |> g | _fa2 |> g. That is, the AA marks 20M1, 20M2,
With a configuration in which the distance L to the primary focus surface 32 is large with respect to the focal lengths f _a1 and f _a2 , the distance g between the mask 18 and the wafer 19 is small, and one of the AA marks is a convex lens and the other is a concave lens. is there.

On the upper side of FIG. 4, the incident light flux is made into a focused light flux with the positive power of the AA mark 20M1, and the AA mark 20W1 is irradiated with the light flux before reaching the focusing point F _1.
The primary focus surface 3 is further increased by the negative power of the mark 20W1.
Focal length f _{b1 of the} AA mark 20W1 imaged on
Is the lens formula

[0041]

[Equation 3] To be satisfied. Similarly, in the lower side of FIG. 4, the incident light beam is changed to a light beam diverging from F ₂ which is a point on the incident side by the negative power of the AA mark 20M2, and this is changed to A
The A mark 20W2 is irradiated and focused on the primary focus surface 32 by the positive power of the AA mark 20W2. The focal length f _b2 of the AA mark 20W2 at this time is

[0042]

[Equation 4] To be satisfied. Under the above configuration conditions, the imaging magnification of the AA mark 20W1 with respect to the condensed image of the AA mark 20M1 is obviously positive magnification from the figure. The direction of the shift amount Δσ of the wafer 19 and the direction of the light spot displacement amount S ₁ of the primary focus surface 32 are opposite, and the shift magnification β ₁ defined above is negative. Similarly, the imaging magnification of the AA mark 20W2 with respect to the point image (virtual image) of the AA mark 20M2 is negative, and the deviation amount Δσ of the wafer 19 and the light spot displacement amount S ₂ on the primary focus surface 32 are in the same direction. , The shift magnification β ₂ becomes positive.

Therefore, with respect to the relative displacement amount Δσ between the mask 18 and the wafer 19, the AA diffracted light 26 of the system of the AA marks 20M1 and 20W1 and the system of the AA marks 20M2 and 20W2.
The shift amounts S ₁ and S ₂ of −1.26-2 are opposite to each other. That is, the spot 3 on the primary focus plane 32 formed by the diffraction of the patterns of the AA marks 20M1 and 20W1.
0 and the spot 31 on the primary focus surface 32 formed by diffraction of the patterns of the AA marks 20M2 and 20W2 change depending on the amount of positional deviation between the mask 18 and the wafer 19, and the two spots 30 and 31 AA line sensor 12 of the light receiving means 11 by the light receiving lens 10
It is projected on the surface. Then, the AA line sensor 12 detects the spot interval between the two spots 30 and 31 to detect the relative displacement between the mask 18 and the wafer 19.

FIG. 6 is a schematic view of the two spots 30 and 31 formed on the surface of the sensor 12 at this time.

In this embodiment, even if the wafer 19 is tilted with respect to the mask 18, two spots 30,
Since 31 moves on the primary focus surface 32 in the same direction and by the same amount, the spot interval does not change, and as a result, a position detection error does not occur.

The above is the configuration of the position detecting means according to the present invention.

Next, in the present invention, the mask 18 and the wafer 1
A method for detecting the surface spacing with respect to 9 will be described with reference to FIG.

In the figure, the same elements as those shown in FIGS. 1 to 3 are designated by the same reference numerals.

In this embodiment, the incident light 15 is made incident on the two AF marks 21M1 (21M3) on the mask 18 surface. The light incident on the AF mark 21M1 (21M3) is diffracted by the mark and, for example, the first-order diffracted light is specularly reflected on the surface of the wafer 19 which is separated from the mask 18 by a distance g ₁ (g ₂ ) and the AF mark on the surface of the mask 18 It is incident on 21M2 (21M4). The AF mark 21M2 (21M4) is composed of a pattern in which the diffracted light has the same focusing action as the lens. The light reflected by the wafer 19 is the AF mark 21M.
2 (21M4) has an optical action such that the outgoing angle of the outgoing diffracted light changes depending on the incoming position (pupil position of the grating area).

For example, when the surface distance between the mask 18 and the wafer 19 is g ₂ , the AF diffracted light diffracted by the AF mark travels along the optical path shown by the solid line and passes through the light receiving lens 10 to form two spots on the surface of the AF line sensor 13. 51 and 52 are formed. Similarly, when the surface spacing is g ₁ , the AF diffracted light diffracted by the AF mark travels along the optical path indicated by the dotted line to form two spots 53 and 54 on the surface of the AF line sensor 13.

FIG. 6 is a schematic view of the two spots 51 and 52 formed on the surface of the sensor 13 at this time.

As described above, the distance between the two spots formed on the surface of the AF line sensor 13 changes depending on the distance between the mask 18 and the wafer 19. Therefore, the distance between the two spots at this time is measured to obtain the mask 18 and the mask 18. Wafer 19
The surface spacing between and is detected.

Next, a method of detecting the relative position between the light projecting means (alignment head 14) and the mask 18 which is the first object, which is a feature of this embodiment, will be described.

First, a method for accurately projecting the light beam from the light projecting device to a position within a predetermined range in the position detection direction (also referred to as alignment direction, AA direction, y direction) will be described.

At this time, the AA mark 20 for position detection is used.
Light flux (diffracted light) 26-1, 26-2 through M, 20W
Using. In this embodiment, a pair of A on the mask 18 surface
Two light beams 26 generated on the surface of the line sensor 12 when the light beam center in the y direction of the light beam from the alignment head 14 is located at the midpoint of the A marks 20M1 and 20M2 in the y direction, here, at the center of the AF mark 21M.
A pair of AA marks 2 so that the light amount distributions of -1, 26-2 (for example, distribution shape or light amount integrated value) are substantially equal to each other.
0M1, 20M2, and a pair of AA marks 20W1,
An opening area of 20 W2 or the like is set.

In this embodiment, as shown in FIG. 6, of the light flux from the light projecting means, the light flux 2 through the AA mark 20M1 on the mask 18 surface and the AA mark 20W1 on the wafer 19 surface.
6-1 and the alignment head 14 so that the integrated values of the light amount distribution on the surface of the line sensor 12 by the AA mark 20M2 on the surface of the mask 18 and the light beam 26-2 via the AA mark 20W2 on the surface of the wafer 19 become equal to each other. Is driven to adjust its position, and the incident position on the mask 18 of the light flux 15 therefrom is adjusted.

In this way, the integrated values of the light quantity distributions of the two light beams 26-1 and 26-2 on the surface of the line sensor 12 are made equal to each other, whereby the projection means, that is, the light beam 15 is positioned in the AA direction. It is carried out. In reality, even if the aperture areas of the AA marks 20M1 and 20M2 are equal and the aperture areas of the AA marks 20W1 and 20W2 are equal, the light amount is vignetted due to the aperture due to the design difference between the left and right AA marks, and the two light fluxes. 26-1,2
There may be a difference in the light amount of 6-2.

In this case, however, the amount of light known in advance may be taken into consideration in designing, and the light amount balance may be considered as follows, for example.

In the case of this embodiment, as is clear from FIG. 4, the AA mark 20M1 having the same opening area on the mask 18 surface.
20M2 is arranged. At this time, the AA mark 20W having the same size as the AA mark on the mask is also formed on the wafer 19 surface.
1, 20W2 are installed, the AA mark 20M1 has a convex lens action with a focal length f _a1 > 0, so that all diffracted light is incident on the AA mark 20W1.

On the other hand, the AA mark 20M2 has a focal length f _a2
Since it has a concave lens action of <0, the diffracted light spreads while A
It is incident on the A mark 20W2. For this reason, the amount of light that spreads beyond the mark size will be vignetting.

The vignetting amount at this time is the AA mark 20M2.
Assuming a plane wave is incident on the AA mark 20M
2,20W2 mark size L _M2 , L _W2 , AA mark 2
0M2 power, AA mark 20M2 and AA mark 20
It is determined by the surface spacing (gap spacing) g of W2, and this amount may be quantitatively calculated and taken into consideration when comparing the light amount distributions of the light beams 26-1 and 26-2.

Now, assuming that the lens action of each AA mark is only in the plane of FIG. 4 (the action of a cylindrical lens, which is not in the direction perpendicular to the paper surface), the effective luminous flux of the AA mark 20W2 is the AA mark 20M2. The light intensity is

[0063]

[Equation 5] Doubled.

Therefore, the light quantity of the diffracted light beam by the AA marks 20M1 and 20W1 may be multiplied by k.

By thus balancing the integrated light amounts of the two light beams 26-1 and 26-2 on the surface of the line sensor 12, the projection light beam 15 in the AA direction of the light projecting means can be positioned.

Instead of balancing the integrated light quantity, 2
The system may be configured to position the light flux 15 so that the distribution shapes of the light quantity distributions of the two light fluxes 26-1 and 26-2 are similar (the same in some cases) or symmetrical.

Next, a method for accurately projecting the light beam from the light projecting means in a predetermined range in the direction orthogonal to the AA direction (x direction) will be described. At this time, the luminous flux 2 for detecting the surface spacing
7-1 and 27-2 are used. That is, the AF mark 21M
1 to 21M4.

In this embodiment, when the center of the light beam 15 in the x direction of the light beam 15 from the alignment head 14 is incident on the mask 18 near the boundary between the set of AF marks 21M1 and 21M2 and the set of 21M3 and 21M4. A pair of AF marks 21M1, 21M2 and a pair of AFs so that the light amount distributions (for example, distribution shape and light amount integrated value) of the two light fluxes 27-1 and 27-2 generated on the surface of the sensor 13 become equal.
The opening areas of the marks 21M3 and 21M4 are set.

That is, as shown in FIG. 6, of the luminous flux from the light projecting means, the luminous flux 27-1 incident on the line sensor 13 via the pair of AF marks 21M1, 21M2 and the pair of A's.
Line sensor 1 through the F marks 21M3 and 21M4
The light amount distribution of the light beam 27-2 that is incident on the third light beam 3 is made substantially symmetrical, whereby the incident position of the light beam 15 from the alignment head 14 in the x direction is adjusted.

It should be noted that in this embodiment, 2 having the same opening area
The light intensity distributions on the line sensor surface are compared using three marks (AA mark and AF mark), but the light flux is in the middle of the two marks (AA mark 20M1 if the mark is AA mark).
And an intermediate position of 20M2, and in the case of an AF mark, when entering an area of an AF mark 21M1 and 21M3, two light fluxes (light flux 26-1 and light flux 26-2 or light flux 27-1).
And the light flux distribution of the light flux 27-2) are set so as to obtain a predetermined relationship, the opening area and the opening shape of the mark may be different.

Here, the light flux 15 from the alignment head 14 is set to have a symmetrical light intensity distribution in the AA direction (y direction) and in the direction orthogonal to the AA direction (x direction). If it is known, the luminous flux may have an asymmetric intensity distribution.

When the light beam 15 is correctly applied to a predetermined position on the mask 18, the peak outputs of the light amount distributions of the two light beams become the same, or the half widths of the light amount distributions of the two light beams become the same. The peak value and the half width of the light amount distributions of the two light fluxes may be compared with each other.

Next, in this embodiment, the four spots (30, 31, 51, 52) generated on the surface of the light receiving means 11 are used to perform efficient and highly accurate alignment (alignment) and surface spacing (gap) measurement. The procedure to be performed will be described.

First, the luminous flux 1 from the alignment head 14
5 is aligned with the mask 18 with a rough accuracy, and the AA mark 20 and the AF mark 20M, 2
The light beam 15 is projected to 1M.

Next, signals corresponding to the two light patterns formed on the line sensor 13 by the AF marks 21M1 to 21M4 are input from the sensor 13 to the controller, and the controller measures the rough surface distance. By driving a wafer stage (not shown), the surface spacing is adjusted to the extent that alignment measurement is possible.

Next, the AA marks 20M1, 20M2, 20
The signals corresponding to the two light patterns formed on the line sensor 12 by W1 and 20W2 are input from the sensor 12 to the controller, and the controller performs alignment measurement with coarse accuracy and four signals are detected on the surface of the light receiving means 11. The wafer stage (not shown) is moved to a position where it is possible. Then, while comparing the integrated light amounts of the four light beams 26-1 and 26-2 on the surface of the line sensors 12 and 13 and the light beams of the respective sets of 27-1 and 27-2, the integrated light amount of each light beam is The projection positions of the projected light beams 15 on the surface of the mask 18 are aligned so that they are equal.

At this point, the error component due to the deviation of the projected light flux in the alignment measurement and the surface distance measurement is minimized, and in the next step, the alignment head 14 performs the highly accurate alignment measurement and the surface distance measurement, and the mask 18 and the wafer 19 are measured. Gap adjustment and alignment are accurately performed.

Next, as another embodiment of the present invention, the light projecting means (alignment head 16) and the first object (mask 18).
A method of detecting the relative position with respect to only the AF mark will be described.

Specifically, the drive unit scans the alignment head 16 (light flux 15) in the alignment direction to form two light fluxes 27-1 formed on the surface of the line sensor 13.
point y ₁ at which the sum of the light intensity integrated values of a and 27-2a shows a peak
(The incident position of the light flux 15) is determined.

Next, the luminous flux 1 from the alignment head 16
The incident position of 5 is a point y in the y direction which is the alignment direction.
_It is fixed to ₁ , and this time, the alignment head 16 is scanned in the x direction, and the point x ₁ at which the sum of the light amounts of the two light beams 27-1a and 27-2a formed on the surface of the line sensor 13 shows a peak is determined. Ask. The above series of operations is performed as x _n −x _n−1 ,
Repeated until y _n −y _n−1 (n = 2, 3, 4, ...) Is sufficiently small, and the obtained coordinates (x _n , y _n ) when the previous values reach a predetermined allowable value Is the coordinate at which the light beam 15 is positioned.

In another embodiment of the present invention, the alignment head 14 and the mask 18 are positioned by A
It is also possible to use a pair of first and second physical optical elements as AA marks formed in the A direction and the direction orthogonal thereto. FIG. 7 shows an example of the second pair of physical optical elements at this time, and FIG. 8 shows the optical path of the light flux at that time.

In FIG. 7, reference numeral 71M denotes a pair of physical optical elements provided on the surface of the mask 18 and having a physical power of 2
One pair of AA marks 71M1 and 71M2, and 71W is a pair of physical optical elements provided on the surface of the wafer 19 and composed of AA marks 71W1 and 71W2 having optical power.

Next, AA marks 71M and 71W shown in FIG.
And the same AA marks 20M1 and 20M as shown in FIG.
A procedure for performing incident positioning of the projected light beam 15 using 2, 20W1 and 20W2 will be described.

First, as a first example, the AA mark 71M shown in FIG. 7 is replaced with the area of the AF mark 21M shown in FIG. 2, and the AA mark 71W is replaced with the AA mark 20W1 and the AA mark 21W2 on the wafer surface shown in FIG. A case will be described in which it is arranged in the area between and as shown in FIG.

Marks 20M1, 20W1 and 20M2
If the specifications of 20W2 are not changed, the luminous flux from these reaches the sensor 12 and forms spots 30 and 31.

The two light fluxes from the marks 71M1 and 71W1 and the marks 71M2 and 71W2 reach the sensor 13 so that the two light fluxes do not overlap on the sensor and reach the spots 51 and 5.
2 is designed, and the positional deviation of the light beam 15 in the alignment direction is compared by comparing the light amount distributions of the spots 30 and 31.
The positional deviation in the direction orthogonal to the alignment direction is obtained by comparing the light amount distributions of the spots 51 and 52. The specific procedure is the same as that of the first embodiment.

As a second example, AA marks 20M and 20W
A case where the AA marks 71M and 71W are separated from each other will be described.

In this case, in the AA marks 20M and 20W, the projected light flux 15 in the AA direction is the same as that shown in the first embodiment.
Position. After that, the alignment head 14
The projected light flux 15 is moved to the positions of the A marks 71M and 71W, and the projected light flux 15 in the direction orthogonal to the AA direction is positioned using the AA marks 71M and 71W. In this way, the incident position of the projected light beam 15 from the alignment head 14 on the mask 18 can be set appropriately.

The present invention can also be applied to other alignment methods. For example, in JP-A-62-261003, when an incident beam is not accurately applied to a diffraction grating of a mask or a wafer, a pair of diffractions from the mask is caused by a wavefront aberration generated by a cylindrical lens of an optical system. Positioning error occurs in the beat signal formed by the light. Therefore, in order to accurately position the incident beam with respect to the positioning direction in this method, the amplitude of the beat signal obtained by the pair of diffracted light from the mask mark is monitored, and this amplitude on the mask is maximized. It is good to position the incident beam at a certain place.

[0090]

As described above, according to each embodiment, the light beam from the alignment head and the first object are utilized by using the alignment mark used for detecting the relative position between the first object and the second object. By aligning with the first object, the light flux from the alignment head can be accurately incident on the predetermined region of the alignment mark while preventing the pattern arrangement on the first object from becoming complicated. As a result, the first object and the second object The relative position of the object can be detected with high accuracy.

[Brief description of drawings]

FIG. 1 is a schematic view of a main part of a first embodiment of the present invention.

FIG. 2 is an enlarged explanatory view of a part of FIG.

FIG. 3 is an enlarged explanatory view of a part of FIG.

FIG. 4 is an explanatory view of the principle of position deviation detection and surface spacing detection of the position detection device according to the present invention.

FIG. 5 is an explanatory view of the principle of position shift detection and surface spacing detection of the position detection device according to the present invention.

6 is an explanatory diagram showing a line sensor on the surface of the light receiving means 11 of FIG. 1 and a light quantity distribution of an incident light beam.

FIG. 7 is a schematic view showing an alignment mark according to the present invention and an arrangement state of the alignment mark.

FIG. 8 is a schematic view showing an alignment mark according to the present invention and an arrangement state of the alignment mark.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 light source 2 collimator lens 5 lens system 101 light projecting means 6 mirror 10 light receiving lens 11 light receiving means 12 line sensor (first detection surface) 13 line sensor (second detection surface) 14 alignment head 15 incident light beam 18 mask 19 wafer 20M , 20W, 21M, 71M, 71W Physical optics

Claims (5)

[Claims] 1. A method of irradiating a light beam having a predetermined intensity distribution onto a mask alignment pattern and detecting a misalignment between the mask and the wafer using the signal light from the alignment pattern. The deviation of the incident position of the light flux on the mask from a predetermined position is detected, the deviation of the incident position is corrected by aligning the light flux with the mask, and the alignment is performed. A position detecting method, characterized in that the positional deviation between the mask and the wafer is detected by the generated light flux. 2. When the first object and the second object are made to face each other and relative position detection is performed, two sets of the first and second objects are provided on at least one object surface of the first object and the second object. Forming a pair of physical optical elements in the position detection direction and the direction orthogonal thereto,
Among the light fluxes from the light projecting means, a pair of light fluxes A optically affected by the first pair of physical optical elements and the other object plane are guided to a predetermined surface, and the light flux on the predetermined surface is guided. The light amount distribution of the pair of luminous fluxes A is detected, and the pair of luminous flux B optically affected by the second pair of physical optical elements and the other object surface is guided to a predetermined surface, and the predetermined surface is guided. A position detecting device, characterized in that the position between the light projecting means and the one of the objects is set by detecting the light amount distribution of the pair of light beams B above. 3. The pair of first and second pairs of physical optical elements are marks for detecting relative positions of the first object and the second object. Position detection device. 4. When a first object and a second object are opposed to each other and relative position detection is performed, at least one pair of physical optical elements is provided on each of the first object surface and the second object surface. 2 sets are formed on the object plane in the position detection direction and the direction orthogonal thereto, and the light flux from the light projecting means is formed on the first object plane and the second object plane by 1 set.
A pair of diffracted light generated at this time is guided to a predetermined surface through a pair of physical optical elements, and the light flux position of the diffracted light on the predetermined surface is detected by a detection means, thereby detecting the first object and the first object. When detecting the relative position with respect to two objects, the first pair of physical optical elements formed on the one object surface of the light flux from the light projecting means and the other object surface are optically affected. , Detecting the light intensity distribution of the pair of diffracted lights incident on the first detection surface of the detection means and being optically acted by the second pair of physical optical elements and the other object surface, (2) Positions of the light projecting means and the first object or the second object are set by detecting a light intensity distribution of a pair of diffracted lights incident on the detection surface. Detection device. 5. The first pair of physical optical elements are for detecting relative positions of the first object and the second object, and the second pair of physical optical elements are the first pair of physical optical elements. The position detecting device according to claim 4, wherein the relative surface distance between the first object and the second object is detected.